The human nervous system exhibits a sensitivity to certain low-frequency stimuli, as is evident from rocking a baby or relaxing in a rocking chair. In both cases, the maximum soothing effect is obtained for a periodic motion with a frequency near 1/2 Hz. The effect is here called "the 1/2 Hz sensory resonance". In the rocking response, the sensory resonance is excited principally by frequency-coded signals from the vestibular organ. However, the rocking motion also induces body strains, and these are detected by stretch receptors such as Ruffini corpuscules in the skin and muscle spindles throughout the body. In addition, signals may come from cutaneous cold and warmth receptors which report skin temperature variations caused by relative air currents induced by the rocking motion. All these receptors employ frequency coding in their sensory function, and it is believed that their signals are combined and compared with the vestibular nerve signals in an assessment of the somatic state. One may thus expect that the resonance can be excited separately not only through the vestibular nerve, but also through the other sensory modalities mentioned. This notion is supported by the observation that gently stroking of a child with a frequency near 1/2 Hz has a soothing effect as well. Appropriate separate stimulation of the other frequency-coding sensory receptors mentioned is expected to have a similar effect.
The notion has occurred that frequency-coding sensory receptors may perhaps respond to certain artificial stimulations, and that such stimulations could be used to cause excitation of the 1/2 Hz sensory resonance. This indeed can been done, by using externally applied weak electric fields as the artificial stimulus, as discussed in the U.S. patent application Ser. 08/447,394 1!. Autonomic effects of this stimulation have been observed in the form of relaxation, drowsiness, sexual excitement, or tonic smile, depending on the precise electric field frequency near 1/2 Hz used. The question whether the effects are perhaps due to the direct action of the electric field on the brain has been settled by experiments in which localized weak electric fields are applied to areas of the skin away from the head; these experiments showed the same array of autonomic effects. It follows that the electric field acts on certain somatosensory nerves.
A major application of the electric exitation of the resonance is seen in the form of a sleeping aid. The method can further be used by the general public as an aid to relaxation and arousal, and clinically for the control of tremmors and seizures as well as disorders resulting from malfunctions of the autonomic nervous system, such as panic attacks.
Electric fields are subject to polarization effects that bar certain applications. These limitations would be circumvented if the excitation could be done by magnetic rather than electric fields. It is an object of the present invention to provide a method and apparatus for excitation of the 1/2 Hz sensory resonance by oscillatory magnetic fields.
An electromagnetic field apparatus for environmental control is discussed by Grauvogel in U.S. Pat. No. 3,678,337. The apparatus is to re-create indoors the electric and magnetic fields that occur naturally out-of-doors, in the interest of physical and mental well-being. In advancing this notion, Grauvogel overlooks the fact that the earth's magnetic field is not shielded by buildings; therefore, the magnetic part of his apparatus is superfluous in the context of his objective. In Grauvogel's claims, the field of use is stated as "environmental control apparatus".
In U.S. Pat. No. 4,197,851 Fellus shows an apparatus for emitting high-frequency electromagnetic waves with a low intensity such as to avoid significant thermal effects in exposed tissue, employing an "antenna" which is applied closely to the skin via insulation material, in such a manner as to conform to body contours. Bentall, in U.S. Pat. No. 4,611,599 shows an electrical apparatus for influencing a metabolic growth characteristic, wherein a radio frequency electromagnetic field is applied to a subject at a low power level such as not to produce bulk heating of the exposed tissue. The high-frequencies used by Fellus and by Bentall are not suitable for exciting the 1/2 Hz sensory resonance.
A device for influencing subjects by means of pulsed electromagnetic fields has been discussed by Lindemann 2!. His "Centron" device comprises a square wave generator connected to an equiangular spiral coil with two branches. The pulse rate can be chosen from 12 discrete frequencies ranging from 1 to 18 Hz. Comments on the workings of the spiral coil are given by Lindeman 3! in the context of "scalar fields", a notion that happens to be in conflict with modern physics. According to Lindeman 3!, the spiral coil of the Centron involves "a high degree of interaction between the inductance and capacitance, creating what is called a scalar". In spite of the erroneous physical basis presented, the Centron device may indeed affect the nervous system. However, several shortcomings are apparent in the design. First, the spiral coil is woefully inefficient and is therefore wasteful of electric current, a precious commodity in battery-operated devices. It may perhaps be thought that the spiral coil design provides localization of the magnetic field by clever cancellations, but that is not the case; a calculation of the steady asymptotic magnetic field induced by the coil shows that the far field is dominated by a dipole. Second, the frequency range of the device misses the 1/2 Hz sensory resonance alltogether, and the use of preset discrete frequencies hampers exploration of other resonances. Last but not least, the fundamental frequencies and some of the higher harmonics in the square wave produce nuisance signals in the brain, and pose a risk of kindling 4! in subjects with a disposition to epilepsy.
It is an object of the present invention to provide an efficient battery-powered device for inducing magnetic fields for the excitation of the 1/2 Hz sensory resonance without causing irritation to the brain or posing a threat of kindling.
Other devices that emit "scalar" fields for unspecified therapeutic purposes are the Teslar watch and the MicroHarmonizer, distributed by Tools For Exploration in San Rafael, Calif. The Teslar watch emits a pulsed magnetic field at a fixed frequency of 7.83 Hertz, and the MicroHarmonizer can be switched to either 7.83 Hz or 3.91 Hz. Neither device can be tuned to the 1/2 Hz sensory resonance.
There is much public concern about the health effects of low-frequency electromagnetic fields. In response, governments have issued guide lines for manufacturers of electronic equipment. Among these, the Swedish MPRII guide lines are the strictest in the world. For human exposure to low-frequency magnetic fields, MPRII calls for an upper limit of 250 nT in the frequency band from 5 Hz to 2 KHz, and 25 nT in the band from 2 KHz to 400 KHz. In the topical application of localized magnetic fields by coils placed close to the skin, compliance with the MPRII guidelines may require use of a distributed coil, in order to keep the spatial maximum of the field from exceeding the MPRII limit. It is yet a further object of the present invention to provide distributed coils that induce localized magnetic fields.
The brain adapts to nuisance signals by plasticly changing neural circuitry, such as to block these signals from further processing. This effect has been noticed in electric field therapy of insomnia, where the effectiveness of a fixed frequency field wears off after several nights of application. It is an object of the present invention to provide a magnetic field with characteristics such as to minimize this adaptive effect.